A GPU-based multi-criteria optimization algorithm for HDR brachytherapy

Currently in HDR brachytherapy planning, a manual fine-tuning of an objective function is necessary to obtain case-specific valid plans. This study intends to facilitate this process by proposing a patient-specific inverse planning algorithm for HDR prostate brachytherapy: GPU-based multi-criteria optimization (gMCO). Two GPU-based optimization engines including simulated annealing (gSA) and a quasi-Newton optimizer (gL-BFGS) were implemented to compute multiple plans in parallel. After evaluating the equivalence and the computation performance of these two optimization engines, one preferred optimization engine was selected for the gMCO algorithm. Five hundred sixty-two previously treated prostate HDR cases were divided into validation set (100) and test set (462). In the validation set, the number of Pareto optimal plans to achieve the best plan quality was determined for the gMCO algorithm. In the test set, gMCO plans were compared with the physician-approved clinical plans. Over 462 cases, the number of clinically valid plans was 428 (92.6%) for clinical plans and 461 (99.8%) for gMCO plans. The number of valid plans with target V100 coverage greater than 95% was 288 (62.3%) for clinical plans and 414 (89.6%) for gMCO plans. The mean planning time was 9.4 s for the gMCO algorithm to generate 1000 Pareto optimal plans. In conclusion, gL-BFGS is able to compute thousands of SA equivalent treatment plans within a short time frame. Powered by gL-BFGS, an ultra-fast and robust multi-criteria optimization algorithm was implemented for HDR prostate brachytherapy. A large-scale comparison against physician approved clinical plans showed that treatment plan quality could be improved and planning time could be significantly reduced with the proposed gMCO algorithm.Comment: 18 pages, 7 figure

Sensitivity and specificity of detection methods for erythropoietin doping in cyclists

Recombinant human erythropoietin (rHuEPO) is used as doping a substance. Anti-doping efforts include urine and blood testing and monitoring the athlete biological passport (ABP). As data on the performance of these methods are incomplete, this study aimed to evaluate the performance of two common urine assays and the ABP. In a randomized, double-blinded, placebo-controlled trial, 48 trained cyclists received a mean dose of 6000 IU rHuEPO (epoetin beta) or placebo by weekly injection for eight weeks. Seven timed urine and blood samples were collected per subject. Urine samples were analyzed by sarcosyl-PAGE and isoelectric focusing methods in the accredited DoCoLab in Ghent. A selection of samples, including any with false presumptive findings, underwent a second sarcosyl-PAGE confirmation analysis. Hematological parameters were used to construct a module similar to the ABP and analyzed by two evaluators from an Athlete Passport Management Unit. Sensitivity of the sarcosyl-PAGE and isoelectric focusing assays for the detection of erythropoietin abuse were 63.8% and 58.6%, respectively, with a false presumptive finding rate of 4.3% and 6%. None of the false presumptive findings tested positive in the confirmation analysis. Sensitivity was highest between 2 and 6 days after dosing, and dropped rapidly outside this window. Sensitivity of the ABP was 91.3%. Specificity of the urine assays was high; however, the detection window of rHuEPO was narrow, leading to questionable sensitivity. The ABP, integrating longitudinal data, is more sensitive, but there are still subjects that evade detection. Combining these methods might improve performance, but will not resolve all observed shortcomings

Nitrogen in graphite and carbon nanotubes: Magnetism and mobility

We use ab initio methods to study the atomic, electronic, and magnetic structure of nitrogen impurities in graphite and carbon nanotubes. We show that the probable configurations for the N impurity atoms are bridgelike adatoms on graphene sheets/nanotubes, substitutional sites and intercalated N2 molecules. We further calculate the migration energy barrier for an N adatom on the graphite surface and the activation energy for the coalescence of two N adatoms into a molecule, which are 1.1eV and 0.8eV, respectively. We also find that the N adatom has a magnetic moment of 0.6μB and that substitutional N enhances the magnetism of C adatoms on graphite and nanotubes, acting as a general promoter of magnetism in carbon systems.Peer reviewe

Pengaruh Promosi Official Account Alfamart Terhadap Sikap Pengguna LINE Aktif (Studi Eksplanatif Kuantitatif Terhadap Mahasiswa Program Studi Ilmu Komunikasi Universitas Muhammadiyah Surakarta)

Saat ini banyak perusahaan yang memanfaatkan media online, atau situs jejaring sosial sebagai media promosi dan periklanan, karena media tersebut sangat praktis, murah dan efesien untuk bisnis dan promosi. Salah satu perusahaan yang saat ini memanfaatkan media sosial sebagai sarana promosi dan periklanan adalah PT. SUMBER ALFARIA TRIJAYA, Tbk. atau lebih dikenal dimasyarakat sebagai Alfamart. Perusahaan ini bergerak dalam bidang retail minimarket. Pada 1 Agustus 2013, Alfamart meluncurkan akun resmi (Official Account) di aplikasi Instan Massanging (IM) yang sedang naik daun, LINE. Langkah itu menjadikan Alfamart sebagai perusahaan retail pertama di Indonesia yang menggunakan akun resmi di LINE. Dengan demikian Alfamart berharap bisa memperluas komunitas yang dimilikinya dan dapat lebih mudah menyebarkan berbagai informasi kepada masyarakat luas tentang produk yang dimilikinya. Penelitian ini bertujuan untuk mengetahui apakah terdapat pengaruh promosi Official Account Alfamart terhadap sikap pengguna LINE aktif, yaitu Mahasiswa Program Studi Ilmu Komunikasi Universitas Muhammadiyah Surakarta. Metode penelitian yang digunakan dalam penelitian ini adalah studi eksplanatif dengan pendekatan kuantitatif. Jumlah populasi keseluruhan mahasiswa aktif Ilmu Komunikasi dari tahun 2006 sampai dengan 2014 berjumlah 671 mahasiswa. Dari jumlah tersebut diambil sample yang berjumlah 100 mahasisawa, dengan kreteria-kreteria yang sudah ditentukan. Hasil dari penelitian ini adalah, terdapat pengaruh promosi Offcial Account Alfamart terhadap sikap pengguna LINE aktif. Hal ini ditunjukan dengan adanya pengaruh yang siknifikan terhadap sikap pengguna LINE aktif dalam hal, informasi produk dan promosi produk yang ada

Hydrogen-induced magnetism in carbon nanotubes

Spin-polarized density functional theory is used to investigate hydrogen-induced magnetism in single-walled carbon nanotubes (SWNTs). Hydrogen trapped at a carbon vacancy can trigger delocalized π electron spin polarization on semiconducting zigzag SWNTs. Hydrogen pinned by a carbon adatom on the surface of the SWNT can induce spin polarization localized at the carbon adatom, independent of the diameter and chirality of the tube.Peer reviewe

Magnetic properties of vacancies in graphene and single-walled carbon nanotubes

Spin-polarized density functional theory has been used to study the properties of vacancies in a graphene sheet and in single-walled carbon nanotubes (SWNTs). For graphene, we find that the vacancies are magnetic and the symmetry of the sheet is broken by the distortion of an atom next to the vacancy site. We also studied vacancies in four armchair SWNTs from (3,3) to (6,6) and six zigzag SWNTs from (5,0) to (10,0). Our calculations demonstrate that vacancies can change the electronic structure of SWNTs, converting some metallic nanotubes to semiconductors and vice versa. Metallic nanotubes with vacancies exhibit ferro- or ferrimagnetism, whereas some semiconducting nanotubes with vacancies show an antiferromagnetic order. The magnetic properties depend on chiralities of the tubes, the configuration of the vacancy and the concentration of the vacancies.Peer reviewe